Ribosomal protein S1 of E. coli, essential for the initiation of protein synthesis, will be investigated with respect to its effect on the 70s ribosome conformation and binding of IF3. The binding site of tRNA on E. coli rRNA will be examined by isolation and RNA fingerprint analysis of specific fragments of 23s rRNA onto which tRNA has been photoincorporated. The topology of the E. coli ribosome will be investigated using a strain deficient in an RNase involved in processing the 5' end of precursor 16s rRNA. The ribosomal proteins in the neighborhood of the 5' end of the 16s rRNA will be determined. The yeast ribosome structure will be studied by the isolation and characterization of a specific fragment cleaved from the ribosome by RNase treatment which contains 5.8s RNA, the 5' and fragment of 25s rRNA and ribosomal proteins.